We propose to launch the first commercial service enabling physicians at unaffiliated hospitals to directly retrieve their patients' digital images and reports from each other on-demand. Despite significant societal need and market demand, US hospitals remain islands of mutually inaccessible data even as patients move between them. Even the most vulnerable patients remain burdened with carrying their own data from place to place. Radiologist interpretations are impaired without the benefit of historical images for side-by-side comparisons. Other physicians are faced with incomplete information to guide clinical decisions. The problem is only magnified for cancer patients who frequently seek care among multiple providers, inadvertently scattering their records across sites. Any one of such a patient's physicians can access only the subset of imaging data available from his/her island, blunting the impact of imaging on screening, diagnosis and management. In Phase I, we demonstrated the feasibility of a novel approach to clinical connectivity - a peer-to-peer network linking commercial imaging information systems from different vendors across three hospitals in a demanding clinical environment. Efforts to exchange data between hospitals over the last two decades have failed primarily due to their reliance on a central shared data repository. In contrast, our peer-to-peer approach satisfies the privacy, security, data stewardship, trust and independence requirements that competing health systems require to exchange digital clinical data with one another. In Phase II, we will launch the first-of-its-kind local healthcare information infrastructure (LHII), enabling five hospitals among three unaffiliated health systems to directly and securely access each other's digital imaging data. We will focus on the application of this technology to cancer screening, diagnosis and management in particular, and we will develop the additional components required to launch the first such non-proprietary clinical information service built on the basis of open standards. This service will have significant commercial and societal implications for the cost-effective delivery of high quality patient care while bringing to market the first commercial platform to support the federal government's recent call for establishing LHIIs around the country.